1. Filed of the Invention
The present invention relates to a semiconductor storage device including nonvolatile memory, and more particularly, to a semiconductor storage device including nonvolatile memory for storing address information about a faulty area, memory operation setting information, and operation setting information about a semiconductor storage device, or the like.
2. Description of the Related Art
Recently, nonvolatile memory having the function of latching data even at power-off includes flash memory, electrically-rewritable nonvolatile semiconductor memory (EEPROM or the like), and ferroelectric memory (FeRAM).
Such nonvolatile memory can be optimized by storing operation modes of the semiconductor storage device in which the memory is contained. When a deficiency is found in a memory cell, the address of the faulty area is stored, and the information is utilized, thereby replacing the memory cell in the faulty area.
Optimization of the operation mode, replacement of the memory cell in the faulty area, and initialization of memory data or the operation mode are performed by means of storing operation modes and addresses of faulty areas in the nonvolatile memory beforehand, and reading the information from a specific address area after power-on to thus perform desired setting (see JP-A-2002-117692 (pg. 14 and FIG. 1)).
In relation to a related-art semiconductor storage device, when the temperature of heat treatment performed during an assembly processes falls outside a guaranteed temperature at which a memory cell can latch data, replacement of a memory cell in a faulty area becomes impossible. Therefore, for instance, a redundant memory cell is replaced with a physical fuse.
However, in the case of a semiconductor storage device manufactured during a low-temperature assembly process (within the guaranteed temperature at which a memory cell can latch data), it is desirable to store the address of a faulty area in electrically-rewritable nonvolatile memory (EEPROM or the like) and to replace a memory cell in the faulty area even after assembly, to thus make an attempt to greatly enhance yield.
Moreover, there may be a case where storing operation modes or a faulty address in memory (mask ROM or the like) which cannot be rewritten by the user is desired. Such mask ROM or the like is not affected by the temperature of heat treatment during the assembly process, but the data acquired after assembly are unrewritable.
The related-art semiconductor storage device cannot satisfy the foregoing competing requirements simultaneously. Different semiconductor devices must be developed in response to the respective desires, raising a problem of an increase in development cost.